yego.me
💡 Stop wasting time. Read Youtube instead of watch. Download Chrome Extension

Transitioning from counting to multiplying to find area | 3rd grade | Khan Academy


2m read
·Nov 11, 2024

This square is one square unit. So, what is the area of rectangle A? The first thing we're told is that each of these little squares equals one square unit, and then we're asked to find the area of rectangle A. Here's rectangle A, and area is the space that it covers. So how much space does rectangle A cover? How many square units does rectangle A cover?

One way to answer that would be to count how many square units it covers, except they've covered up our square units. So, one idea is we could draw them back. Say you covered them up; we'll draw them back in. So, go in like this, connect all these, and then we should be able to count our square units.

So we have one, two, three, four, five, six, seven, eight, nine, ten, eleven, twelve. Twelve square units! Rectangle A covers 12 square units, so it has an area of 12 square units. But this isn't the only way that we could have solved this. We could have also said, we could have also looked at this and said, okay, this top row is four square units long. One, two, three, four. It has a length of four units, so that means the top row will have one, two, three, four square units inside of it.

Then we could have looked over on the side over here and said, well, how many rows of four will there be? There will be one, two, three rows of four. So we'll have this row of four, and then a second row of four, and a third. So, three times we will have four square units.

There's four square units at the top, another in the middle, and another at the bottom. Three times, we will have four square units. Or we could go even farther than that. We could have said we could have done three times four, or we could look at this and say, okay, here's one column. This column has three square units; it has a length of three. One, two, three.

How many of these columns like this will there be? There will be one, two, three, four, because our length here, but the top is four. So this time four times, we will see three square units—one, two, three—and we'll see that one, two, three, four times.

So no matter which of these we solved, whether we counted the square units like in the beginning or we multiplied the side lengths, the three and the four, in every case we're going to find that this equals 12 square units. The area of rectangle A is 12 square units because it covers 12 square units.

More Articles

View All
Lucy in the Sky with Asteroids | Podcast | Overheard at National Geographic
What sparked my interest in space was just dreaming about the stars. This is Adriana Ocampo, she’s a NASA scientist, and back when she was a kid in Argentina, she’d grab her dog and head to the roof of her house. You know, we would go every evening that w…
a chill day in my life
Good morning guys, it’s currently 11:20 a.m. - answering YouTube comments - okay so now it’s 12 and I think it’s enough scrolling so I’m just gonna delete all of the social media apps because it takes a lot of time. Let’s do my skincare - skincare time -…
Cameras Reveal the Secret Lives of a Mountain Lion Family | Short Film Showcase
Mountain lion, puma, cougar— all names for an animal that has long been misunderstood, feared, hunted, and eliminated from most of its range. The cougar is often believed to be solitary and even heartless, but recently, deep in the Wyoming Wind River Rang…
This Indigenous Practice Fights Fire with Fire | Podcast | Overheard at National Geographic
What you’re hearing is the sound of grass burning in a dense forest in northern California. It’s full of coniferous trees, brush, and shrubs, and tons of branches, and tons of dried out foliage, because the area is so dried up thanks to the warming climat…
Sci-Fi Monsters: Past, Present, Future | StarTalk
Who doesn’t love the zombies? You know, they’re always chasing you. There’s always more of them, and they keep you alert. But also, who doesn’t love a good alien? We all want to meet the aliens. So, when I think of these forces that rise up in the storyt…
Diadochi and the Hellenistic Period | World History | Khan Academy
Where we left off in the last video, Alexander dies in 323 BCE at the young age of 32. Even though he conquered all of this territory, it was a very short-lived Empire. What happens next is a period known as the wars of the Diodi. Let me write down this …